This invention relates to displacement transducers and more particularly to a variable differential transformer transducer employing printed coil configurations.
The prior art is replete with a number of transducer elements which operate to convert from one physical quantity to another. For example, such transducers can operate to convert linear motion measurement into an electrical signal and so on.
A particular transducer is sometimes referred to as a linear variable differential transformer (LVDT). The LVDT is a displacement transducer and it basically produces an electrical output which is proportional to the displacement or movement of a movable core associated with the transducer. Such transducers employ a primary winding to which an AC voltage is applied. Two secondary windings are symetrically spaced from the primary and are usually connected externally in series opposition. As the core moves, the coupling between the primary and the secondary changes and hence, the voltage which is induced in the secondary also changes. In such devices, there is no physical contact between the coil and the core and hence, the devices are capable of operation for extremely long periods as they do not wear out. Such devices have been employed in various forms for decades and are well known.
As indicated above, the present transducers employ multiple coils which are arranged as secondary and primary windings. In order to fabricate such devices, bobbins are employed. A bobbin is a relatively complex machine part and different length and shape bobbins are required to accommodate different types of transducers. As such, the LVDT can be employed to measure relatively small displacements and such devices are sometimes referred to as short travel devices.
In other embodiments, the LVDT is used to measure a large displacement and such devices are referred to as long travel devices. In any event, a long travel device often employs a large number of bobbins in order to accommodate the required displacement. Each bobbin is then wound to accommodate a suitable coil and the winding of such bobbins is a relatively time consuming operation. Once the bobbins are wound, the individual wires in regard to each coil must be connected together and provisions must be provided for external leads or terminals. Thus, in the fabrication of multiple coil units, the wiring and construction of such LVDTs is quite time consuming. This expense, of course, increases as the length of the unit increases and hence, long travel transducers are extremely expensive.
It is an object of the present invention to provide an improved variable differential transformer device which employs printed coil configurations. The individual coil structure can be coupled together rapidly and efficiently to provide various transducer configurations with a minimum of effort. These configurations, as will be described, produce completely unexpected and unanticipated operating characteristics compared to present commercially available devices and with these characteristics there is also a substantial reduction in assembly and labor costs.